Overhead sign crushes car on freeway in Melbourne Australia. 3

[MDEAus]

This happened a few days ago, but the article has just been updated with dash-cam footage from the car immediately behind the one involved.
very quickly it can be seen that the failure point is at the welded joint for the bolted connection. the grainy footage makes things harder to see, the base off the standoff looks weird, why would you close the end off the SHS to be welded to the main beam? Galvanising requires drainage points and a minimum area open between closed sections. Unless that is a solid block off steel? I'm not sure why they would have used a solid block off steel though.

https://www.abc.net.au/news/2019-01-08/tullamarine-freeway-sign-falls-and-crushes-car/10700470

 

[IRstuff]

Here's some screenshots from a better copy of the video; it really doesn't look like anything is obviously broken, though, aside from some sheet metal? Truly amazing that the driver escaped with "minor" injuries.

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[hokie66]

IRstuff,

What's broken are the welds between the two upstands and the gantry horizontal. MDEAus is correct in that the bottoms of those upstands look weird.

 

[MDEAus]

How the driver managed to avoid being crushed is astonishing, if they hadn't swerved the post would have laid down directly over the driver and not to the side.

I don't work with road signage at all but I do work with vehicles and structures made from SHS/RHS, about the only thing I can think off is that the ends weren't capped instead the gantry part now has to holes were the steel has fatigued and torn away around the welds. It looks like a painted/powder-coated structure rather than galvanized which would explain the absence of 'weep holes'.

In typing this I re-watched a news reel of the event and you can see two holes where the sign once stood. So my first though off failed welds was wrong it appears inssufficient strength in the gantry member.

 

[hokie66]

Well, if those dark spots are holes where the upright penetrated, then the connection must have just been fillet welds around the perimeter. So the connection failed, not the gantry member.

 

[MDEAus]

I don't think the upright penetrated the gantry member. I would have thought the short SHS upright would be butt welded to the gantry member. If the SHS member passed through the top of the gantry member I'd have expected buckling of the upright before the sign would have fallen. You can see in the closer image the cracks propagating from the corners of the torn out section. The Gantry member appears to have been to thin to resist fatigue loading from the sign.

 

[human909]

I did find it humorous that the police (Acting Sergeant Jason Lane) said wind was not a factor. He might as well have said gravity wasn't a factor either!

 

[hokie66]

MDEAus,
That would be very thin, and I doubt it. Hopefully, some more information will come through.

 

[MDEAus]

Hopefully more information does come out, unlike in the US NTSB the ATSB only investigates Air, Rail, and Marine incidents. I don't think we will get a publicly released report unless someone files a freedom of information request a few months later.

It would surprise me that it's very thin but that's what it looks like to me. The sign has been in place for a little over 1 year having been installed at the end of 2017. What is concerning is that it was a relatively new structure.

P.S. Acting Sergeant Jason Lane is part off the Highway Patrol.

 

[hokie66]

This is a case where I think we should find out. The press will be like a dog with a bone until there is a result. This failure will be something very simple, as opposed to many transport failures.

 

[IRstuff]

Based on those other pictures, it does not look like it was really bolted to the gantry at all. Had it been bolted, the bolts would have torn 4 holes in addition to the hole from where the welds failed.

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[EdStainless]

It looks to me like the mounting flanges were just fillet welded to the overhead gantry.
In the frames that IRStuff clipped the bolted connections are intact.
I wonder if that type of sign was ever supposed to be mounted there?

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[ACtrafficengr]

Acting Sgt. Lane may have just meant it wasn't windy on the day of the incident.

About 20 years ago, NYSDOT had a series of issues with cracking sign structures. They found that the wind load from trucks passing under them caused excessive movement and resulting fatique. I can't find it, but there was a video of a cantilever sign structure deflecting a foot or more after a box truck passed under it.



My glass has a v/c ratio of 0.5

Maybe the tyranny of Murphy is the penalty for hubris. -

http://xkcd.com/319/

 

[IRstuff]

The overhead shots of the gantry are confusing to me, since the holes, which presumably correspond to the welded columns, are so close to the edge that I can't see how there could have been bolted connections on that side of the sign.

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[thebard3]

In the picture showing the holes from above, I see what looks like a seam where the right red X marker is located. I'm wondering if what we see is only a sheet metal cover that obscures the actual structural members.

Brad Waybright

It's all okay as long as it's okay.

 

[azcats]

https://bigbuild.vic.gov.au/newsfeed/new-gantries-installed-over-the-monash

No real info above. Just some good video of a similar, recently installed sign. To me, it appears the large gantry is fabricated from plate. Who knows if there's any internal structure. Should have run that HSS 'stub' through the whole member and not just attached it to the outside.

 

[msquared48]

Well, that's what you get when you drive on the wrong side of the road and the sign is mounted backwords...

Mike McCann, PE, SE (WA)

 

[oldestguy]

My bet is it was near quitting time when was set. Plan was to come back tomorrow to weld or bolt it. Come tomorrow another job took precedence. Of course none of us members here ever were in that situation.

 

[hokie66]

IRstuff,

There were no bolts to the gantry. There was a welded stool with an end plate, and the sign uprights were end plate bolted to that. The stool, end plates, and bolts all went down with the sign. The welded connections of the stools failed, whether in the welds or in the base metal of the gantry.

It will be most interesting to me to find out if there was divided responsibility between the gantry and the sign supports. I have designed some gantries, not like that one, but over major highways. But I can't recall having designed the attachment of signs.

 

[NorthCivil]

Australia's having a bad summer isn't it?

I'm with oldestguy. the lack of deformed material leads me to believe that the connection wasn't completed.

I guess the lesson here would be that if you have hundreds of welds to check, and can't be bothered, request a welding inspector to be hired to check them all?